[mkdltn]

I think there are two blues. A light blue and a dark blue. The light blue pass for this card appears to be absent but the dark blue is there in the background. I downloaded the scan of the Wiltse card from the LOC site which has poor register which gives clues to the cards color makeup. The image below is a blownup view of the corner where all the different color passes that make up the background can be seen. Your beater seems to have a lighter background since the gray and light blue are gone. Could this be from an aborted print run?
Perhaps the light blue, Pink and Gray the final colors in the card.